Low Fidelity Prototype
Our idea started from a cuckoo clock. During our brainstorming session for mechanisms to spin the hands of the clock and to make the bird come out every hour, we realized that we overestimated the time and resources we had so eventually ended up forgoing the bird idea.
Focusing on the gear train system so that the hour hand will only spin 1/12 of the minute hand (Mechanism #24), we first designed and adjusted the ratios of the gears on the gear generator. We laser cut them with cardboard boxes and considering the gear sizes, we cut out the front and back faces.
Then we drilled three holes into each face for which the dowels will be placed. The dowels connect the gears and assist them spinning. The positions of the holes were a rough estimate, so after we assembled everything with all the gears and dowels, the dowels were not perfectly parallel to each other and the gears didn’t align that well. We also made a crank out of cardboard boxes and attached a handle which was connected to one of the rods sticking out of the back face of the clock.
One of the main challenges while making the low fidelity prototype was figuring out how to mount the minute and hour hands. Since they have to be attached to the same rod (center of the clock) but rotate at different speeds, it was difficult to come up with a way to do so. For the low fidelity, we attached a straw to the hole of the main hour gear (the leftmost front one), so that it sticks out of the front face. The hour hand was then attached to the straw. The main hour gear rotates independently from the connected rod and small gear behind, which should rotate in the speed of the minute hand. Therefore, the minute hand is directly connected to the rod.
minute hand on rod, hour hand on straw
Mid Fidelity Prototype
Laser-cutting the Housing Components and Gears
After getting a general idea of how our model will be assembled and function, we started on actually laser cutting the woods to make gears and clock faces. Instead of a rectangular shape we did for low fidelity, we decided on using hinges for the sides so the clock face can be close to a circle.
We laser cut two for each gear to stack them up which gives more surface of contact between gears and rigidity. Cutting the hinges and clock faces required much more effort and time. For the clock faces, we made three holes on each of them and ensured the positions are very precise based on the gear generator file. For the hinges, we used the file from the makercase website and adjusted the shape and size accordingly. The original file had two pieces of hinge that connect to each other to go around the circle but since we wanted it to be four sides, we had to divide the given hinge into half and manually draw the joints with Adobe illustrator. We tried out a test cut first with 0.004’’ kerf which fit pretty well so we decided to go with this.
When using the laser cutter, we set the diameter of the clock face to be 12 inches but somehow the machine printed them way larger and happened to be more than 15 inches. The hinges were also bigger than we aimed it to be (but we didn’t re-print to save wood).
Assembling and Mounting
Assembling the hinges and the faces was truly one of the hardest parts of this project. The joints of the hinges were so fragile and had tension so that a very gentle touch could make the structure collapse. Even if we paid extra attention assembling these components, one of the joints snapped so we ended up applying wood glue instead. Some of the sides did not perfectly fit as we expected from the test print because of the tension of the hinges and curved structure we didn’t account for.
We also assembled the gears as we worked on the housing structure. We aligned the gears much better than the low fidelity prototype, which we tested and were able to see the gears spinning smoothly as the other ones spin.
Final Prototype
A design decision was made to leave one quarter of the walls open in the final project. This decision was motivated by two fronts: to show off the interior gear train of the system which we thought would be interesting to viewers, and to increase access while assembling the gear train. The mid-fidelity prototype informed us about the structural sensitivity of the housing structure (clock faces and hinges) so we wanted to avoid large scale movements like putting on another hinge after the gear train is in place.
limited space to access the gear trains
Structure Assembly & Post-processing
Since every part of the project needed to be mounted on the total structure, the hinges and clock faces had to be completed first which included decorating the faces as well as post-processing the hinges.
Given that this project was due mid-October, we decided to go for a Halloween theme for the clock face. Both faces and the hinges were orbital sanded to remove laser marks. Since the front face would be where most people focused on, Halloween themed vinyl stickers were posted on the frontal face and then removed after spray painting both faces black to reveal the designs in the negative space. Said negative spaces on the front face were then stained with teak oil before a clear coat was applied to both faces including the interior which would also be visible with the new open design. The hinges were stained with teak wood on the inside and outside to preserve the cool look of the laser cut lines and protect the wood. We also took this time to stain the duplo gears, washers, and dowels. The housing structure was then reassembled after everything dried with wood glue between the joints for added strength.
Gear Alignment
The next step was installing the gear train. Since the housing structure was delicate and finalized, we only had one shot at getting everything right; any error may be catastrophic especially with the small working window. Therefore it was imperative that we constantly test-mounted before securing the gears and dowel positions. It was a good thing we tested first before anything was glued down because we discovered a massive problem immediately. When realigning the gear train contact angles for better overlay of the minute and hour gears, we had actually overlapped an axle with the traversal path of another gear, inhibiting the gear from turning.
However, because the clock face holes have already been cut and processed, we couldn’t modify it further, this is the arrangement we’ve got. Fortunately, we adapted quickly and decided to cut off the impeding axle before it hits the gear and install a supporting stand within the structure that would hold it in place instead of the hole in the clock face. After cutting a few iterations of the stand adjusting for fitting of lap joint, curved base of attachment, and stand height, everything was attached through a vigorous process of testing, gluing, then testing again.
The prolonged installation took much longer than anticipated and we were in the OEDK deep into the night. Around 2 AM, one of our worst nightmares occurred where a wooden washer serving as an end cap for the shortened axis accidentally attached to the stand, inhibiting rotation entirely. Thanks to how tight wood glue is after hardening, there was no way we could pry it loose so we had to conduct ‘surgery’ on the piece with a dremel and vacuum within the small space and grind away the entire washer to restore motion.
What remained was to simply attach the minute hands which were filed, sandblasted, then clear coated after water jet cutting to their respective points. The short hour hand attached to the tube of the hour gear protruding and the long minute hand directly attached to the axle of the minute gear. With an easy attachment of the handle and vacuuming some dust away, everything was complete.
our final prototype
Cost Analysis
The following cost analysis is only for the fabrication of the final product. This excludes materials cost for earlier prototypes and iterations.
| Cost Type | Cost | Price | Quantity | Source | Total |
| Labor | Base
Labor |
$15 / h | 8h/day * 10 days * 2 people | $2,400.00 | |
| Laser Cutter | $18.01 / h | 5h | Indeed | $90.05 | |
| Waterjet Cutter | $18.50 / h | 45 min (including design) | Salary Expert | $13.88 | |
| Spray Painter | $15.25 / h | 3 including stain | Velvet Jobs | $45.75 | |
| Materials | Plywood | $29.88 /
8ft x 4ft sheet |
3.5 sheets | Home Depot | $104.58 |
| ¼” Dowels | $5.29/25 | 3 dowels | Amazon | $00.63 | |
| Aluminum | $22.14 / 1ft2 | ¼ sheet | GetMetals | $5.54 | |
| Total | $2,660.43 | ||||
Links below are slides for each step of prototyping and demonstration video.
slides:
demo video:
https://drive.google.com/file/d/1WFQtMbFR-HcNbVfkL2b_wgXQKIZI9VLc/view?usp=drive_link
